In a hermetic refrigeration compressor, the motor is often protected by a temperature responsive overload protector. The protector is typically mounted within or against the stator and interrupts the supply current to the motor in response to its temperature rising to a predetermined limit.
When the overload protector is mounted against the stator, an electrically insulating material is typically provided to separate the protector from the stator to avoid direct electrical contact therebetween. This same electrically insulating material, however, also acts as a thermal insulator that reduces the effectiveness of the protector. U.S. Pat. Nos. 4,163,913; 4,236,092; 4,503,347; and 4,567,390 disclose this insulating material as denoted by reference numerals 30, 54, 52, and 50 respectively.
In addition, a close fit between the mating surfaces of the protector and the stator becomes critical when the overload protector is mounted against the stator. A poor fit, often caused by human error during assembly, affects the heat transfer to the protector which may result in inadequate protection of the compressor. Moreover, the close fit requirement often limits the selection of temperature sensors to those having flat surfaces that correspond to certain flat surfaces of the stator, thus limiting the choice of mounting locations within the compressor.
Another problem associated with overload protectors mounted within the hermetic shell of a refrigeration compressor is the protector's exposure to cold suction gas and other relatively cold compressor components. The cooler surroundings within the compressor shell tend to lower the temperature of the protector and thus reduce its sensitivity to heat generated by the stator. Of the four patents mentioned above, only the '347 patent comes close to addressing this problem. The '347 patent discloses an abutment post 78 which protectively stands between the temperature sensor and a relative cold cover 44. None of the four patents disclose an overload protector receptacle having a heat retaining shield facing in a direction opposite the stator.
Therefore, it is an object of this invention to provide an overload protector receptacle that shields its temperature responsive protector from cold suction gas and other relatively cold parts of the compressor.
Another object is to provide a receptacle that includes a heat retaining shield that traps heated refrigerant around the overload protector, thereby eliminating the need for close fitting contact between the overload protector and the stator.
Another object is to provide a receptacle that can position an overload protector in a variety of positions, including over the axial end of the rotor.
Yet another object is to provide a receptacle adapted to hold a variety of overload protectors having various shapes.
These and other objects will be apparent from the attached drawings and the description of the preferred embodiments that follow below.